This application claims the priority of German Patent Application, Ser. No. 200 09 382.7, filed May 25, 2000, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
The present invention relates, in general, to a roofing membrane.
Conventional roofing membranes typically include a support layer and a plurality of strips arranged in spaced-apart disposition on one side of the support layer and made of bituminous material to enable a gluing of individual roofing membranes. The strips are separated from one another by a layer of scattered material and covered by a fusible film. The fusible film is arranged upon the roofing membrane over the entire surface of the side that carries the strips of material. As a consequence, moisture can accumulate in the area of the layer of scattered material between the individual strips of bituminous material between the film and the layer of scattered material. As the roofing membrane is processed, the film is difficult to flame in this area especially since the film is only loosely applied over the layer of scattered material.
The bituminous strips on the bottom side of the roofing membrane can be interrupted in longitudinal extension of the membrane so that a controlled vapor pressure equalization is ensured. The interruptions of a strip are hereby offset in relation to the interruptions of a neighboring strip.
The strips of bituminous material are made, for example, of heat-sensitive self-adhesive bitumen (WSKB). The used bitumen suffers, however, shortcomings because once the roofing membrane is glued together, increased heat exposure through solar radiation results in a softening of the strips. This, in turn, may lead to bubble formation underneath the roofing membrane.
It would therefore be desirable and advantageous to provide an improved roofing membrane to obviate prior art shortcomings.
According to one aspect of the present invention, a roofing membrane includes at least one support layer, a plurality of strips arranged in spaced-apart disposition on at least one side of the support layer and made of bituminous material, wherein the strips of bituminous material have a penetration depth between about 120 and 170 at a temperature of 50xc2x0 C., and a softening point between about 100xc2x0 C. and 110xc2x0 C., a layer of scattered material separating the bituminous strips from one another, and a fusible film which covers the strips of bituminous material and is composed of a plurality of film strips which are oriented in parallel relationship to the bituminous strips but not interconnected.
To ensure clarity, it is necessary to establish the definition of several important terms and expressions that will be used throughout this disclosure. The term xe2x80x9cpenetration depthxe2x80x9d relates to DIN [German Industrial Standard] 52 010 and is determined here at a temperature of 50xc2x0 C. The penetration depth, indicated in units of {fraction (1/10)} mm, denotes the depth of a needle to penetrate the bituminous material within five seconds. The term xe2x80x9csoftening pointxe2x80x9d relates to DIN 52 011 and is the measured softening point of ring and ball (R.a.B. method).
The bituminous material may be made, for example, of up to about 65% of straight-run bitumen, up to about 15% of oxidation bitumen, up to about 10% of block polymer styrene butadiene and up to about 10% of oleoresins.
The support layer may be multilayered, e.g. with the outermost layer of the support layer on top side of the roofing membrane and the layer on the bottom side of the roofing membrane made of a coat of sand as layer of scattered material.
Bituminous strips of this type retain their shape even when exposed to intense solar radiation. Moreover, these material properties enable a rapid liquefaction of the strips and thus a convenient handling of the roofing membrane.
As the fusible film is composed of a plurality of separate strips, moisture is able to escape via at least small interstices between the individual film strips and thus prevented from accumulating between the film and the support layer. Therefore, the film can easily be melted away when the roofing membrane is welded.
The strips of bituminous material may be arranged on the bottom side only, on both sides, or on the top side only, of the roofing membrane. When applied only on the top side of the roofing membrane, bituminous material is also always applied upon the bottom side of the membrane, however, not in the form of strips but e.g. in full contact over the entire area. When the underside of the roofing membrane is in full contact with bituminous material, the fusible film is placed over the bituminous material in single-piece configuration. This embodiment is applicable, when the roofing membrane is intended for application upon trapezoidal metal sheets. In this case, a maximum gluing surface can be established between the trapezoidal metal sheet and the roofing membrane.
In particular, when the strips of bituminous material are arranged upon the bottom side of the roofing membrane, the film strips may be separated from one another by a breach. In this way, moisture can escape via the thus-shaped slot, suitably incorporated at the manufacturer""s end. When the strips of bituminous material are applied upon the top side of the roofing membrane, it may be suitable that the film strips essentially cover only the strips of bituminous material. This may be realized, for example, at the manufacturer""s end, where a film is initially applied over the entire membrane surface and then removed in the regions between the strips, e.g. by means of hot air. In these regions, the layer of scattered material on the support layer is exposed.
All strips of bituminous material arranged upon the top side of the roofing membrane may extend over an entire length of the roofing membrane. Compared to interrupted strips, a greater gluing surface can hereby be made available. The provision of a vapor pressure equalization is secondary here because of the subjacent layer, typically a plate-shaped heat insulation, in the produced state of the roofing membrane.
According to another feature of the present invention, the bituminous strips upon the bottom side of the roofing membrane may be discontinuous in longitudinal direction of the roofing membrane. In this way, bubble formation is prevented once the roofing membrane is placed, and a pressure equalization can be realized over the entire roof area. The strips, positioned at the edge of the roofing membrane are, however, of continuous configuration also upon the bottom side of the roofing membrane.
According to another feature of the present invention, the bituminous strips may cover at least 50% of the side of the support layer, thereby realizing a good gluing capability of the roofing membrane.
According to another feature of the present invention, the bituminous strips may have varying width. A membrane side may have strips of a width of 2 to 2.5 cm and strips of a width of about 8 cm. This configuration may be applied, for example, when welding a roofing membrane with another overlapping roofing membrane, so as to realize a continuous welding seam with a width of about 8 cm. It is also conceivable to apply upon the top side of the membrane bituminous strips of same width, e.g. 8 cm (represents the standard seam width between two adjoining overlapping membranes).
According to another feature of the present invention, the bituminous strips may have a grooved surface.
According to another feature of the present invention, the film may be needled.